Coin identification methods are often used for the purposes of determining the denomination and authenticity of coins and often for the purposes of mechanically discriminating coins based on that information. The most common coin discrimination devices, such as those used in automatic vending machines, coin-to-currency changers, gaming devices such as slot machines, bus or subway token “fare boxes”, and the like, generally employ inductive coin testing methods to determine the denomination and authenticity of coins. These methods typically work by measuring the effect of a coin on an alternating electromagnetic field produced by one or more coils disposed at a passage through which a coin passes. The effect of the coin on the impedance of the coil(s) is dependent on one or more of the properties of the coin such as diameter, thickness, conductivity and permeability. The detection signals output from coil sensors of this type are concentrated in a basic pattern representative of these characteristics of the coin. By comparing the measured pattern with patterns established in advance, the genuine or counterfeit nature of the coin, and the denomination of the coin, can be determined.
More recently, optical sensors have been implemented to provide another method, or additional criteria, by which the denomination and authenticity of a coin may be determined. Optical sensor methods have been primarily directed towards the discrimination among coins of similar electromagnetic and physical properties, yet not authentic with respect to a specific sovereignty, such as coins originating from a foreign country or entity. In such methods, an optical sensor typically captures a two-dimensional image of a coin surface such as one of the faces, the periphery, or the ridge of the coin which is then used to perform pattern matching by comparing the acquired coin image to patterns of known coins to produce a discrimination signal. However, little effort has been directed towards the automated identification of coinage features deliberately minted, yet not universally present on coins of the same denomination or type, such as details indicating the date and the location of mint of a coin. Such information is desirable as it can be a source of novelty, entertainment and appreciation. Additionally, certain coins of particular date and mint are considered “rare” and are thus more valuable than coins of similar denomination yet produced with a differing date or mint. Currently, identifying and retrieving coins of specific date and mint from general circulation is difficult and time consuming. Date and mint information is typically determined “by eye,” sometimes with the aid of magnification, and can often be taxing on the individual as the examination of a large number of coins can be tedious and time consuming. There is currently no device which automates the identification of these coin attributes, nor one which can do so at high speed and low cost.
Prior art has been directed towards capturing an image of a side of a coin, generating a binary image and discriminating the coin based on geometric relations among patterns detected in the binary image. In one such method, identification is based on the radius, number and area of connected regions and the distances between those connected regions; by comparing these measured values with those of known coins the authenticity and denomination of the coin is determined. However, methods of this type are insufficient for the robust identification of patterns not universally present on the denomination or type of coin detected, such as patterns indicative of the date and mint, which can have a plurality of shapes and features which subtly differ. For similar reasons, methods in which coin image data is highly abstracted, often in order to reduce computational complexity, prove insufficient to extract the desired coin attributes.
Much of the prior art makes use of the fact that coins can have authenticity and denomination specific information on the edge, periphery, or on both sides (obverse and reverse) of a coin, and thus the coin only needs to be imaged from one vantage point to determine the denomination and genuine nature of the coin. However, when date and mint information are present on a coin, that information tends to be present on only one side of the coin, thus both sides of a coin often need to be imaged to extract the desired information from the proper side of the coin. The need to capture and process images of both sides of a coin produces non-trivial difficulties which are not adequately overcome by the prior art, which are addressed by the invention described herein.
Prior art has been directed towards the use of MOS-type image sensors to capture coin images. MOS-type image sensors often suffer from blurring effects and geometrical distortion caused by the ‘rolling shutter’ of such sensors. One method overcomes these limitations by using an image acquisition method in which the image capture phase begins in advance, before a coin reaches a prescribed position, at which point the coin is briefly illuminated and the image capture is concluded. In several embodiments presented herein, rolling shutter issues arising from the use of MOS-type sensors are circumvented using a different, simpler method.
Prior art has been directed towards measuring the damage, or wear, of a coin using captured images of the sides of the coin. In one method, coins are advanced using a conveyor system; magnetic and image sensor data is then acquired of the coins and compared to data patterns of known coins. Other methods are aimed at the replication and automation of the grading processes used in the collectables industry to determine the quality of known coins. The methods and apparatuses described therein are generally unsuitable for the purposes of the present invention described herein.
Prior art has been directed towards converting circular images of coins into rectangular images and comparing those rectangular images to reference images for the purpose of determining the genuine or spurious nature of the coins. However, such methods produce non-linear spatial distortions that make robust identification difficult, especially for subtle details such as date and mint information. The method described herein does not require the transformation of circular images to rectangular images.
Prior art has been directed towards verifying the embossed nature of an imaged coin using special illumination and image processing methods. Such methods are also not necessary for the purposes of the invention described herein.
Devices capable of extracting denomination, type, date and mint information from coins may be used for the sorting of coins by such attributes as well as used to augment current devices that employ coin discrimination such as coin counters which typically aid untrained members of the general public in the conversion of their coins to cash. Such an augmented coin counting device could provide the return, compensation or redemption of users' coins deemed “rare” or valuable as well as provide entertainment for users of such devices and a means for promotion and loyalty for such devices. Such an augmented coin counting device may provide a sweepstakes-like experience for users as they are made aware of, or rewarded for, coins with additional value, be it collectible value, promotional value, monetary value, or otherwise, that the users were previously unaware of. Such an augmented coin counting device may provide entertainment to users which may be used to distinguish the device from that of competing products or services.
Prior art has been directed towards coin identification for the purpose of promotion and encouraging the use of coin counting kiosks. However the method described requires the minting and distribution of non-government issued promotional coins for which the winning/losing nature of the promotional coins cannot be visually determined. In said method, the winning/losing nature of a coin is made manifest only upon deposit into a coin counting kiosk, which detects, and discriminates on, the unique inductive signature of the promotional coin. The promotional methods described herein use the visual features of government issued coins, which do not require the additional minting and distribution efforts as the promotional coins described in the prior art, and for which the winning/losing nature, or relative place in a spectrum of rewards of the coin, can be visually determined prior to deposit.
Other uses for devices capable of extracting denomination, type, date and mint information from coins may be the aid in “vintage surveys” of coins in circulation conducted by central banks, minting agencies, government and academic authorities, etc. in which a large sample of coins is taken and the date and mint data is collected to determine statistics about the circulating money supply. Other areas of use may include sorting, entertainment, promotion or gaming.